Kokua Line June Watanabe

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Pesky weeds gumming up Kawainui Marsh

Question: When is the government going to clean out the Salvinia molesta in the Kawainui Marsh? Along Kapaa Quarry Road, you can't see the water at all because of this plant. There used to be kingfisher birds perched above waiting for prey, but they have disappeared since they can't get through the weeds.

Answer: State and city officials are well aware of the Salvinia molesta in Kawainui Marsh.

The salvinia is not as bad as it once was at Wahiawa's Lake Wilson, where it now appears to be under control, and birds and other wildlife are not considered in danger because of it.

However, the salvinia growing in roadside ditches along Kawainui Marsh "is a recurrent maintenance issue," said Larry Leopardi, chief of the city Division of Road Maintenance.

The division "has repeatedly removed the salvinia and will continue to do so," he said. Removal was scheduled this week, using a backhoe outfitted with a skimming basket, he said yesterday.

"As far as we are concerned, it is an ongoing maintenance and removal effort that saps our limited maintenance resources," he said.

Crews regularly check the shoulders of Kapaa Quarry Road and "perform maintenance several times a month," he said. "Salvinia is not the only concern" -- sometimes there are illegal dumpings to be dealt with, as well.

If you feel the growth has gotten out of hand, call the Kailua Corporation Yard at 262-4346.

In addition to the salvinia, there are several other species of floating weeds in Kawainui Marsh, said Mindy Wilkinson, alien and invasive species coordinator with the state Department of Land and Natural Resources.

But, the belted kingfisher is not being pushed out by the overgrowth -- "it's just that they very rarely migrate out to Hawaii," she said.

A "better guess as to what might be getting excluded from the water" by the floating weed would be night herons (aukuu)," she said. Even if so, the herons are a common Hawaii bird.

One thing Kawainui Marsh has that Lake Wilson does not is a connection to the ocean. Salvinia is not tolerant of salty or brackish water.

"As the winter storms flush surface plants more toward the canal there at the north side of Kailua, the plants will be exposed to a level of salt as they approach the ocean that will kill them," Wilkinson said.

Although salvinia does cover the surface of the fresher water at the inland end, the brackish water helps to keep it under some control.

At this point the salvinia is considered "more of a management issue" rather than a danger to wildlife. There is a plan to dredge the marsh to increase water-bird habitats.

"What I've suggested and hope they will eventually implement is changing the water flow in those ponds so they are brackish, which won't harm the native water birds, but which will suppress plants and weeds like salvinia that are not native and also not salt-tolerant," Wilkinson said.